The automation of transmission functions is acquiring increasing significance; automatic manual transmissions, which demonstrate such automation, present the advantage, that the driver is relieved of the task of changing gears in the vehicle. Thereby, a generally more comfortable and safer operation is made possible. Furthermore, automatic manual transmissions present significant cost advantages. In this regard, when clutch movement occurs, a translational movement is normally transferred to the release bearing of the clutch through a corresponding electro-mechanical actuator according to the state of the technology. Similar configurations are also used for shifting automation, whereby for selection and shifting two kinematically independent movements are necessary, which are conducted by electromechanical transmission discs in the manner of the state of the technology.
Electro-mechanical actuators are also used for shifting between two wheel drive and four wheel drive for partially four wheel driven vehicles. For example, from DE 42 30 326 A1 an electronic selector mechanism for vehicle transmissions is known, in which an intermediate gear for a four wheel drive presents two separate electronic movement mechanisms, namely a regional movement mechanism and a clutch movement mechanism. In this regard, a regional movement mechanism serves to shift the intermediate gear between an upper region, a neutral position, and a lower region; the clutch movement mechanism controls the engagement of a clutch between two wheel drive, automatic drive, and four wheel drive. According to DE 42 30 326 A1, the regional movement mechanism comprises an electric motor, which is constructed co-axially relative to an output shaft of the intermediate gear, as well as a linear screw, to convert the rotational movement of the motor shaft selectively into an axial movement of the regional sliding clutch.
The electrical drive for the selector function in an automatic manual transmission is normally realized with a brush motor. In this regard the rotational movement of the brush motor is converted to a translational movement with a transmission (spindle, worm gear, gear rack), which leads directly to shifting direction selection; it is also possible that through the translational movement, a slotted lever is moved for the preliminary selection of a certain path for the shifting action.
The selector lever movement is a movement with little force requirement, whereby only the frictional torque and moment of inertia within the selector mechanism must be overcome, so that the conversion of the motor's rotational movement into a translational movement known, according to the state of the technology, is comparatively expensive for this purpose.
Furthermore, the requirements for positioning in the current shifting direction, depending on the configuration and number of shifting directions, are quite high and require a sufficient of resolution of sensor elements as well as an exact algorithm for positioning. The usually selected conversion between motor rotational movement and translational movement has the goal of keeping the requirement on the resolution of a movement sensor technically realizable; the realization of high conversion is connected in a disadvantageous manner with high constructive expenditure.
The present invention has the task of reporting a selector drive for automatic manual transmissions of motor vehicles, which avoids the disadvantages of the state of the technology. In particular, simple positioning should be made possible and the constructive expenditure should be reduced. Moreover, a method for the selection of a selector position in the selector mechanism of an automatic manual transmission of a motor vehicle is reported, which is especially suitable for the operation of the selector drive according to the invention.